The application relates to a semiconductor device and to a method for producing a semiconductor device. The semiconductor device includes a semiconductor body with a semiconductor device structure including at least a first and a second electrode. Between the two electrodes, a drift region is arranged, the drift region including charge compensation zones and drift zones arranged substantially parallel to one another.
Such semiconductor devices are known under the generic designation of compensation semiconductor devices and are characterized by a relatively low on-state resistance based on the higher doping of the drift zones in the drift region, which is made possible by the parallel arrangement of charge compensation zones with complementary doping. For certain applications, such as zero voltage switching (ZVS) resonance converters, a high switching speed of the body diode is desirable in such compensation semiconductor devices, e.g. the CoolMOS, in order to avoid the destruction of the device at low applied loads or in particular fault conditions of such a converter.
This requires the controlled, effective and stable reduction of carrier flooding in the diode operation mode in such compensation semiconductor devices. If the compensation semiconductor device is optimized to a minimum on-state resistance Ron·A, the field distribution in the de-commutation process of the semiconductor device is such that an interruption of the diode reverse current cannot be avoided. One cause for this lies in the fact that the whole semiconductor region between the compensation columns lies in a depletion region even at very low voltages between source and drain, with the result that no flood charges are available in the device even in an early stage of a diode commutation.
The diode reverse current is therefore interrupted abruptly, leading to high voltage peaks up to oscillations and thus to the possibility of a premature destruction of the device. This happens primarily in a fast de-commutation process of the body diode of a compensation semiconductor device. The better the compensation, i.e. the higher the doping level and the less the distance between the columns, the more violent will be the interruption. Compensation semiconductor devices optimized as MOS switches are therefore not suitable for use as fast recovery epitaxial diode field effect transistors (FREDFET) if the focus of the application lies on the switching behavior of the diode.
The switching behavior can be improved slightly for fast commutation by reducing the lifetime of the charge carriers. There is however a limit to the level of the flood charges available for the adjustment of switching behavior. A further method for the improvement of the switching behavior of a ZVS (zero voltage switching) resonance converter is to delay the switching transistor in its switch-on behavior. This is achieved by switching on the transistor with a relatively high series resistance, resulting in a correspondingly small current change in the diode commutation process. Such a series resistance, however, causes undesirably high dynamic losses.